Generally, due to the fact that a fan motor is mounted inside the refrigerator in order to make forced circulation of air cooled in a heat exchanger, the motor needs to be waterproof for preventing moisture condensed in accordance with temperature fall in the refrigerator from permeating into the motor.
The conventional motor is illustrated referring to FIG. 7 which shows lateral cross-sectional view of the motor according to the prior art.
As shown the figure, the fan motor comprises a stator 2, a rotor 3, a circuit board 7, a rotation shaft 6, a bearing 5 and end brackets 4. The stator 2 is combined with a bobbin 2b with coil wound. The bobbin is on the side of a stacked core 2a in which a plurality of lamination sheets are stacked so as to have constant thickness. The rotor 3 has a cylinder-shaped permanent magnet inserted through the stacked core 2a. The circuit board 7 is placed toward the side of the stator 2 and makes magnetic fields around the stacked core 2a by applying electric currents to the coil and rotating the rotor 3. The rotation shaft 6 is forcibly fixed through the center of the rotor 3 and transmits driving forces. The bearing 5 is to enable the rotating shaft 6 to rotate at a fixed position. The end brackets 4 are combined at both sides of the stacked core 2a respectively.
The conventional fan motor in the refrigerator is insulated by molding and is also capable of waterproof against the moisture because it is made by an insert molding method applied over the stator 2 and the circuit board 7.
This kind of fan motor is usually put in a casing for the motor and is fixed on the inner side wall of the refrigerator. Thus, this motor has a compact size to be accepted into the casing and has a torque enough to make air circulation in the refrigerator.
In particular, the enough torque is more important because refrigerators these days are being much larger. Generally, the torque of the motor is proportional to a diameter of a rotor assuming that the other conditions are same. The fact that the conventional motor is classified to “a motor of an inner rotor” in which the rotor 3 rotates inside the stator 2, results in an increased size of the motor in case that the rotor has bigger size to get the enough torque.
The bigger size of the motor gives rise to increased costs due to spending more materials such as molding resin and iron sheets. Also, the motor takes up more space to be mounted in the refrigerator.